"We are analyzing them at present," Kupriyanov said in a prepared statement. "The current problems at Sakhalin-2, including ecological problems, will be taken into consideration when making a decision."

Gazprom had been negotiating to join the project with a stake of just over 25 percent.

Russian regulators have steadily turned up the pressure on the development. The day before Friday's meeting, the Natural Resources Ministry announced that water protection authorities had suspended the licenses of a subcontractor.

Since the summer, the ministry and prosecutors have repeatedly criticized the Shell-led consortium for allegedly silting rivers and illegal logging, threatening to revoke a key ecological permit that could halt work.

Observers contend that the pressure is aimed at securing more favorable terms for Gazprom to join the project, in line with a government strategy of expanding the state's control over the nation's energy reserves.

Shell enraged the Kremlin last year when it announced that the cost of the project would double to $22 billion: Under the terms of a production sharing agreement, signed in the 1990s, the Russian government only sees revenues from the Sakhalin-2 project when its costs have been covered.